Nuni Widiarti, Lisnawaty Simatupang, Kerista Tarigan, Dimas Gilang Ramadhani
The oxygen evolution reaction (OER) remains the kinetic bottleneck in alkaline water splitting, motivating the design of oxide-based catalysts that combine strong redox activity, efficient charge transport, and interfacial stability. In this study, we develop a hierarchical density functional theory (DFT) screening framework that connects heterogeneous reduced graphene oxide (rGO) support chemistry, single-oxide anchoring, directional heterointerface assembly, defect engineering, and final OER free-energy analysis within a unified atomistic design strategy. The results show that NiO and ZnO do not favor the same anchoring environment on rGO: NiO is preferentially stabilized near oxygen-rich epoxy motifs, whereas ZnO is favored at vacancy-rich sites. This anchoring asymmetry enables the directional construction of the NiO-on-ZnO/rGO heterostructure, which exhibits the most favorable interfacial stabilization, charge redistribution, and near-Fermi electronic activation among the tested architectures. Defect screening further identifies interface-centered hydroxylation and oxygen-vacancy motifs as the most promising pre-active configurations, outperforming isolated oxide defects in both defect energetics and charge-transfer response. OER free-energy analysis on reconstructed NiOOH-like active-state models reveals that D4-NiOOH Interface and D3-NiOOH Ni-site are the two co-leading catalytic motifs, each delivering a theoretical overpotential of 0.17 V within the present DFT framework, substantially lower than pristine NiO and pristine ZnO. Overall, the study demonstrates that support heterogeneity, asymmetric anchoring, interface-centered defect activation, and NiOOH-like active-state formation together define a useful design principle for defect-engineered NiO-ZnO/rGO OER catalysts. © 2026 The Authors
Chemistry Education Study Program, Faculty of Mathematics and Natural Sciences, Universitas Negeri Semarang, Semarang, Indonesia; Department of Chemistry, Faculty of Mathematics and Natural Sciences, Universitas Negeri Medan, Medan, Indonesia; Department of Physics, Faculty of Mathematics and Natural Sciences, Universitas Sumatera Utara, Medan, Indonesia
